The present invention relates to a rear support adjustment device particularly usable in ski boots.
The problem of achieving optimum support for the skier's calf once the boot has been put on, is currently felt.
U.S. Pat., No. 3,729,841, in fact discloses a ski boot having an upper quarter which is transversely articulated at a recess defined at the rear end of the boot.
Said upper quarter can rotate only about its axis, thus following the inclination of the skier's leg.
The disadvantage of this solution consists of the fact that the upper quarter is a rigid supporting element for the leg during the extension step, and thus once the maximum angle of rotation is attained it cannot cushion impacts on the calf in any way.
A similar disadvantage is observed in U.S. Pat. No. 3,945,135, which describes a ski boot having a vertical bar to which an upper quarter is transversely and rotatably articulated.
A U.S. Pat. No. 4,030,214 is also known, disclosing a boot which comprises a semi-rigid shell which is provided, in a rearward position, with a vertical notch to the side of which openings are defined for the insertion of a slider which is adapted to limit the deformation of the flaps of said notch.
A more or-less rigid rear support is obtained according to the position of the slider.
The disadvantage of these solutions consists of the fact that when the flaps are opened the supporting action on the calf is lacking from the upper edge of the quarter up to the position of the slider.
Safe support is furthermore not always provided, due to the friction which occurs between the inner shoe and the flaps, which causes a closing return thereof which is not always correct.
Similar remarks can be made for U.S. Pat. No. 4,073,073, which describes a device by means of which the user can use the leg while walking by opening the upper and rear part of the quarter.
This solution is obtained by means of the combination of a central slot, which is obtained from the upper part of the quarter and the enlarged edges of which act as guide for a slider composed of two parts, with a plate arranged inside the quarter and with an eccentric element for the loosening and tightening of said slider.
French patent, no. 2,358,119, is also known which describes a ski boot the rear quarter whereof is divided into three elements which are mutually partially movable by virtue of the presence of a notch defined transversely to said rear quarter.
This solution has disadvantages, since it can be used only for a forward flexing of the quarter, whereas for a backward flexing it allows no optimum support of the calf, since the individual elements can in practice slide only forward with respect to one another.
Each element, in fact, has a step-like discontinuity which abuts on a further underlying step-like discontinuity.
However, this also entails difficulties in execution, since during molding there are many undercuts which complicate extraction from the mold.
It is furthermore observed that during forward flexing it is possible to have a deformation of the material (splaying of the openings) which can lead to the formation of yield lines which, besides damaging the quarter, hinder its overall aesthetic appearance.